3988. The store received, respectively, 20, 15 and 10 coats of three different firms. It is known that the share of high-quality products among the products of the first company is on average 70%, the second 80% and the third 60%. At random, the chosen coat was bad. Find the probability that it is supplied by the second firm.

Detailed solution. Decorated in Microsoft Word 2003 (Quest decided to use the formula editor)